They are attempting to overturn a Lords amendment to the Employment Bill giving compensation for BNP members judged to be expelled unfairly from a union.
Labour MP Tony Lloyd said unions should be allowed to limit membership "only to those who share their beliefs".
But BNP leader Nick Griffin said it was a "totalitarian" move aimed at excluding Labour's political opponents.
Mr Griffin told BBC Radio 4's Today programme: "We feel this is a piece of very unpleasant, totalitarian legislation and it's not about trade unionists being able to decide who else is in the union really.
"This is about the Labour Party giving its allies in the top of the union movement, the opportunity to throw out people, not so much that they don't agree with, but who are standing with a different political agenda to the Labour Party.
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